Biomedical subjects
Publications and source records attributed to G T Mencher.
The level of maturation of the auditory system markedly affects the results of all forms of infant hearing screening. The same test repeated in two weeks may yield significantly different results. The paper reviews some of the maturational changes which occur, considers male/female differences, and offers some normative developmental information about the preterm infant.
There is very limited information available about hearing loss in children in Latin America and in Central America in particular. Costa Rica is a peaceful, well-organized country with an excellent health care system and a very good infrastructure of roads, programs, and services. It served as the site for a four-phase study to determine the incidence and prevalence rate for sensorineural hearing loss in children in that region of the world. The four phases involved (1) screening over 12,500 children in the public schools, (2) examining those enrolled at programs for the hearing impaired, (3) searching the community for children not in schools or special programs, and (4) an extensive questionnaire designed to obtain basic demographic data about hearing-impaired children in the country. Included were questions about age of identification, etiology, and hearing aid use. Results of phases 1 and 2 are reported here. Using a 1.368 per 1,000 live birth average (a figure reported for 36 nations), the projected number of hearing-impaired children in Costa Rica should be about 1,068. After concluding the first two phases of the study, it was determined that the actual number of hearing-impaired children in Costa Rica is between 1,174 and 1,274. That is a ratio of between 1.50 and 1.63 hearing impaired per 1,000 live births, well within the ranges reported elsewhere. Since this is the first national study of a Latin American country, that information is significant, suggesting that the general prevalence of hearing loss in that part of the world is the same as in the developed nations of Europe and North America.
To determine the effects of white noise as a pretest sensitizer in neonatal hearing screening, 450 neonates were tested under 18 test conditions which also permitted examination of infant state and criterion stimuli (warble tone versus narrow band noise) as variables. There were three pretest conditions: No pretest sensitizer; 90 dB pretest sensitizer, and 100 dB pretest sensitizer. Each pretest condition was followed by either a 90 or a 100 dB criterion stimulus. Analysis concerned an increase in the number and in the strength of the responses. Generally, there was no benefit associated with the use of white noise as a pretest sensitizer.
A study of 56 severely asphyxiated infants (8 hearing impaired and 46 normally hearing) was designed to identify specific markers associated with asphyxia which could be related to hearing loss. Sixteen variables, including such items as: one- and five-minute Apgar scores, muscle tone, use of a ventilator, prolonged stay in the NICU, hypoxic-ischemic encephalopathy (HIE), other organ damage, and intra-uterine growth retardation (IUGR) were considered. Results suggested four factors related to asphyxia which are often found in the presence of hearing loss, but none of these was considered a definitive marker or predictor of such a disability. A combination of HIE, seizures, associated organ damage and IUGR should be considered a strong marker for the probability of a sensorineural hearing loss.
Listing the eight most important aspects of epidemiological research relevant to hearing loss, this paper reviews some of the difficulties encountered in trying to do such research in the developing world. Various research formats are discussed. This paper concludes with a review of what has been reported in the world's literature about the incidence and prevalence of sensorineural hearing loss in children. The average finding from 34 nations is 1.368 hearing impaired per 1,000.
Explore the source record for details and available documents.